Implement UMA log throttling for cellular connections

chrome/browser/io_thread.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_IO_THREAD_H_
 #define CHROME_BROWSER_IO_THREAD_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 272 matching lines @@
   void ClearHostCache();
 
   void InitializeNetworkSessionParams(net::HttpNetworkSession::Params* params);
 
   base::TimeTicks creation_time() const;
 
   // Returns true if QUIC should be enabled for data reduction proxy, either as
   // a result of a field trial or a command line flag.
   static bool ShouldEnableQuicForDataReductionProxy();
 
+  // Returns the callback fro updating data use prefs.
+  const metrics::UpdateUsagePrefCallbackType GetMetricsDataUseForwarder();

[Alexei Svitkine (slow), 2016/04/05 15:58:57]

Nit: Return by const ref.

[gayane -on leave until 09-2017, 2016/04/05 17:24:45]

Done.

+
  private:
   // Map from name to value for all parameters associate with a field trial.
   typedef std::map<std::string, std::string> VariationParameters;
 
   // Provide SystemURLRequestContextGetter with access to
   // InitSystemRequestContext().
   friend class SystemURLRequestContextGetter;
 
   friend class test::IOThreadPeer;
 
@@ skipping 288 matching lines @@
       system_url_request_context_getter_;
 
   // True if SPDY is disabled by policy.
   bool is_spdy_disabled_by_policy_;
 
   // True if QUIC is allowed by policy.
   bool is_quic_allowed_by_policy_;
 
   const base::TimeTicks creation_time_;
 
+  // Callback for updating data use prefs which needs to be initialized on UI
+  // thread and passed to |ChromeNetworkDelegate|.
+  metrics::UpdateUsagePrefCallbackType metrics_data_use_forwarder_;
+
   base::WeakPtrFactory<IOThread> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(IOThread);
 };
 
 #endif  // CHROME_BROWSER_IO_THREAD_H_